Elementary module for a fuel cell

ABSTRACT

An elementary module including an oxidation unit for generating electrons by oxidizing a fuel with an oxidant, an anode and cathode sandwiching an electrolytic membrane, an anode block including a fuel transporter support for transporting an anode feed flow containing the fuel to an anode chamber and an anode electron collector attached to the fuel transporter support, a cathode block including an oxidant transporter support for transporting a cathode feed flow containing the oxidant to a cathode chamber and a cathode electron collector attached to the oxidant transporter support, the elementary module defining the anode chamber, respectively, the cathode chamber, between the oxidation unit and the fuel transporter support, respectively, the oxidant transporter support, the anode electron collector, respectively, the cathode electron collector and the oxidation unit being attached by bonding and electrically connected by means of an anode conductive bridge, respectively, a cathode conductive bridge, containing an electrically conductive adhesive.

The present invention relates to an elementary module of a fuel cell andalso to a fuel cell including at least one elementary module.

Two main types of fuel cells are known for generating an electriccurrent by oxidation of a fuel, generally of dihydrogen, with anoxidant, generally dioxygen.

A first group of cells is formed from “planar” cells as described in FR3 000 615 A1 and WO 2011/079377 A1. Such fuel cells are slim, theirlengths and widths being large relative to their respective thicknesses.They are generally fed with dioxygen by natural convection and theirpower is low, limited to a maximum of 100 W.

A second group of cells is constituted by cells including a plurality ofthin elementary modules each extending in a longitudinal direction,stacked on top of each other and electrically connected in series. Eachelementary module includes an oxidation unit formed from an anode and acathode sandwiching an electrolytic membrane, the oxidation unit itselfbeing sandwiched between bipolar plates which ensure, firstly, thefeeding of the cathode of an elementary module with a flow containingthe oxidant and the feeding of the anode of the contiguous elementarymodule with a flow containing the fuel, and, secondly, the electricalconnection of the oxidation units, acting as anode and cathode electroncollectors.

In order to reduce the contact electrical resistances between theoxidation units and the bipolar plates, and to ensure the fuelleaktightness, the bipolar plates are pressed against the oxidationunits, conventionally by means of compression tie rods connected to endplates sandwiching all of the elementary modules, for example asdescribed in US 2005/0095485 A1. As a variant, WO 2013/134789 A1describes a fuel cell including a compression belt surrounding andcompressing an assembly constituted of two end plates sandwiching astack of elementary modules. WO 03/083977 A1 describes a fuel cellincluding a stack of elementary modules housed in a case including a boxand a lid to close the box, the height of the housing being less thanthe height of the stack before closure of the case. The box and the lidbear complementary reliefs, such that by click-fastening the lid ontothe box, a compression is applied to the stack.

However, to ensure the compression of the stack of elementary modules inthe fuel cells of the prior art, it proves to be necessary to use heavyelements, such as end plates or a case, thus reducing the power densityper unit mass of the cell, which is defined as the ratio of the powerthat is able to be generated by the cell to the mass of the cell.Moreover, the bipolar plates used in the cells of the prior artgenerally have complex shapes, necessitating numerous complex andexpensive manufacturing steps.

There is thus a need for a fuel cell that can overcome the drawbacksmentioned previously.

To this end, the invention proposes, according to a first of itsaspects, an elementary module that is useful for a fuel cell, theelementary module including:

-   -   an oxidation unit configured to generate electrons by means of        the oxidation of a fuel, preferably of dihydrogen, with an        oxidant, preferably dioxygen, the oxidation unit including an        anode and a cathode sandwiching an electrolytic membrane,    -   an anode block including a fuel transporter support suitable for        transporting an anode feed flow containing the fuel to an anode        chamber, and an anode electron collector attached to the fuel        transporter support,    -   an oxidant transporter support suitable for transporting a        cathode feed flow containing the oxidant to a cathode chamber,        and a cathode electron collector attached to the oxidant        transporter support,    -   the elementary module being configured so as to define the anode        chamber, respectively, the cathode chamber, between the        oxidation unit and the fuel transporter support, respectively,        the oxidant transporter support,        the anode electron collector, respectively, the cathode electron        collector, and the oxidation unit being both attached by bonding        and electrically connected to each other by means of an anode        conductive bridge, respectively, a cathode conductive bridge,        containing an electrically conductive adhesive.

Advantageously, a cell including at least one elementary moduleaccording to the first aspect of the invention does not require anycompression means such as those of the prior art to ensure a goodelectrical connection between the anode and the anode electroncollector, on the one hand, and between the cathode and the cathodeelectron collector, on the other hand. In particular, the anode andcathode conductive bridges provide a perfect electrical contact betweenthe anode electron collectors and cathode electron collector,respectively, and the oxidation unit. The elementary module according tothe invention thus has a low total electrical resistance withoutapplication of external compression. This low total resistance is partlylinked to the low contact resistances internal to the elementary module.In addition, the anode and cathode conductive bridges provide, at leastpartially, or even entirely, the mechanical strength of the elementarymodule, by rigidly connecting the anode and cathode blocks to theelectrolysis unit. Moreover, the total mass of the anode and cathodeconductive bridges is low with respect to the mass of the means requiredto ensure the compression of a cell of the same volume and including thesame number of elementary modules as a cell of the prior art. Thus, acell including an elementary module according to the first aspect of theinvention has a higher power density per unit mass.

Moreover, the oxidation unit and the fuel transporter support may beboth attached by bonding to each other and electrically insulated fromeach other by means of an anode leakproofing bridge containing afuel-leaktight electrically insulating adhesive,

the anode leakproofing bridge being configured so that the anode feedflow transported to the anode chamber flows essentially from the fueltransporter support directly to the anode. Besides the leaktightnessthat it ensures, as will emerge more clearly hereinbelow, the anodeleakproofing bridge may advantageously participate in the mechanicalstrength of the elementary module.

According to a second of its aspects, the invention also relates to anelementary module that is useful for a fuel cell, the elementary moduleincluding:

-   -   an oxidation unit configured to generate electrons by means of        the oxidation of a fuel, preferably of dihydrogen, with an        oxidant, preferably dioxygen, the oxidation unit including an        anode,    -   a fuel transporter support that is suitable for transporting an        anode feed flow including the fuel to an anode chamber,    -   the module being configured so as to define said anode chamber        between the anode and the fuel transporter support,    -   the oxidation unit and the fuel transporter support being both        attached by bonding to each other and electrically insulated        from each other by means of an anode leakproofing bridge        containing a fuel-leaktight electrically insulating adhesive,    -   the anode leakproofing bridge being configured so that when the        anode feed flow is transported to the anode chamber by the fuel        transporter support, said anode feed flow flows essentially from        the fuel transporter support directly to the anode.

Advantageously, a cell including at least one elementary moduleaccording to the second aspect of the invention does not require anycompression means such as those of the prior art to ensure theleaktightness of the fuel cell. In particular, the anode leakproofingbridge ensures that the fuel entering the anode chamber by means of thefuel transporter support reaches the anode while ensuring that it doesnot leak out of the anode chamber. Moreover, within a fuel cellincluding a plurality of elementary modules according to the secondaspect of the invention, the total mass of the anode leakproofingbridges is low with respect to the mass of the means required to ensurethe compression of a cell of the same volume and including the samenumber of elementary modules as a cell of the prior art. For a massidentical to that of a cell of the prior art, a cell including at leastone elementary module according to the second aspect of the inventionthus has a higher power density per unit mass.

In addition, the oxidation unit may include an electrolytic membrane incontact with the anode, the anode being placed between the anode chamberand the electrolytic membrane, and optionally an anode collecting layerin contact with one face of the anode placed facing the anode chamber.

Moreover, the elementary module may include a cathode block including anoxidant transporter support that is suitable for introducing a cathodefeed flow containing the oxidant into a cathode chamber,

-   -   the oxidation unit including a cathode placed in contact with        the electrolytic membrane, the electrolytic membrane being        sandwiched between the anode and the cathode,    -   the module being configured so as to define said cathode chamber        between the cathode and the oxidant transporter support,    -   the oxidation unit and the oxidant transporter support being        both attached by bonding to each other and electrically        insulated from each other by means of a cathode attachment        bridge containing an electrically insulating adhesive.

The elementary module may include an anode block including the anodeelectron collector attached to the fuel transporter support, and thecathode block may include a cathode electron collector attached to theoxidant transporter support,

-   -   the anode electron collector, respectively, the cathode electron        collector and the oxidation unit being both attached by bonding        and electrically connected to each other by means of an anode        conductive bridge, respectively, a cathode conductive bridge,        containing an electrically conductive adhesive.

The invention also relates to a fuel cell including an elementary moduleaccording to either of the first and second aspects of the invention, ora plurality of elementary modules stacked on top of each other in astacking direction, at least one, preferably all, of the elementarymodules of the plurality each being according to either of the firstand/or second aspects of the invention.

The invention relates to a fuel cell including a plurality of elementarymodules stacked on top of each other in a stacking direction, at leastone, preferably all, of the elementary modules of the pluralityincluding:

-   -   an oxidation unit configured to generate electrons by means of        the oxidation of a fuel, preferably of dihydrogen, with an        oxidant, preferably dioxygen, the oxidation unit including an        anode and a cathode sandwiching an electrolytic membrane,    -   an anode block including a fuel transporter support suitable for        transporting an anode feed flow containing the fuel to an anode        chamber, and an anode electron collector attached to the fuel        transporter support,    -   a cathode block including an oxidant transporter support        suitable for transporting a cathode feed flow containing the        oxidant to a cathode chamber, and a cathode electron collector        attached to the oxidant transporter support,    -   the at least one elementary module being configured so as to        define the anode chamber, respectively, the cathode chamber,        between the oxidation unit and the fuel transporter support,        respectively, the oxidant transporter support,    -   the anode block, respectively, the cathode block and the        oxidation unit being attached to each other, and/or the at least        one elementary module being such that, prior to the assembly of        the at least one elementary module in the plurality of        elementary modules of the fuel cell, the anode block,        respectively, the cathode block and the oxidation unit are        attached to each other.

The fuel cell according to the invention does not require anycompression means to ensure the electrical connection between theelementary modules and the fuel-leaktightness of each elementary module.It thus has a power density per unit mass that is higher than that of afuel cell of the same mass of the prior art.

Moreover, since an elementary module of the fuel cell is not compressedby an external force other than the potential weight of other elementarymodules placed vertically above said elementary module, said elementarymodule is easy to change in the case where said elementary module isdefective. Notably, as will emerge more clearly hereinbelow, twoconsecutive elementary modules may be separated from each other in thestacking direction. The elementary module may thus be easily extractedfrom the fuel cell by sliding it in a transverse direction with respectto the stacking direction. The elementary module may be removable.

For the purposes of the present invention, it is considered that twomembers, for example the anode block or the cathode block, on the onehand, and the oxidation unit, on the other hand, are attached to eachother when another member rigidly connects said two members. Forexample, said other member is an adhesive bridge, a screw or a rivet. Onthe contrary, for example, the assembly of two parallel plates heldtogether by the application of a compression force normal to their facesdoes not define an attachment for the purposes of the invention, sincethe plates may notably be moved relative to each other when thecompression force is taken away.

Preferably, the anode block, respectively, the cathode block and theoxidation unit are attached to each other by means of an attachmentmember placed, at least partially, or even entirely, between the anodeblock, respectively, the cathode block and the oxidation unit.

The attachment member may include, or even may be constituted by, anelectrically conductive or electrically insulating adhesive.

The attachment member may be attached via at least one of its faces tothe anode block, respectively, to the cathode block and to the oxidationunit. Preferably, it is attached, via two of its faces which areopposite each other, to the anode block, respectively, to the cathodeblock and to the oxidation unit.

The attachment member may be placed between the anode block,respectively, the cathode block, and the oxidation unit and may includean electrically conductive adhesive, so as to define an anode conductivebridge, respectively, a cathode conductive bridge.

The attachment member may be placed between the cathode block and theoxidation unit and may include an electrically insulating adhesive, soas to define a cathode attachment bridge.

The attachment member may be placed between the anode block and theoxidation unit and may include an electrically insulating adhesive, soas to define an anode leakproofing bridge.

Preferably, the anode block, respectively, the cathode block and theoxidation unit are attached by bonding and electrically connected toeach other by means of an anode conductive bridge, respectively, acathode conductive bridge, containing an electrically conductiveadhesive.

Preferably, the anode block, respectively, the cathode block includes ananode electron collector attached to the fuel transporter support,respectively, a cathode electron collector attached to the oxidanttransporter support, the anode conductive bridge and the anode electroncollector, respectively, the cathode conductive bridge and the cathodeelectron collector being both attached by bonding and electricallyconnected to each other.

Preferably, the oxidation unit and the fuel transporter support are bothattached by bonding to each other and electrically insulated from eachother by means of an anode leakproofing bridge containing afuel-leaktight electrically insulating adhesive, the anode leakproofingbridge being configured such that the anode feed flow transported to theanode chamber flows essentially directly from the fuel transportersupport to the anode.

Finally, the invention relates to apparatus, notably chosen from aflying object, for example a drone, a bicycle and an electric generator,for example a charger for electrically recharging a set of mobiledevices, said apparatus including a fuel cell according to theinvention.

The elementary module and the fuel cell according to any of the aspectsof the invention described above may also include one or more of thefeatures described hereinbelow.

Preferably, the elementary module is “planar”, i.e. it generally extendsin a longitudinal plane. A planar elementary module is particularlysuitable for forming a fuel cell stack. In particular, the elementarymodule may be “slim”, i.e. its thickness, defined as being the meanvalue of the distances, measured in a direction transverse to thelongitudinal plane, between two opposite longitudinal outer faces of theelementary module, is at least 50 times smaller and preferably at least2500 times smaller than the length of the elementary module, measured inthe longitudinal plane.

In particular, the length and/or width and/or thickness of theelementary module may be, respectively, between 10 mm and 500 mm,between 10 mm and 500 mm, and between 0.2 mm and 2 mm. Preferably, theopposite longitudinal outer faces of the elementary module are parallel.

Moreover, when the oxidation block is fed with fuel and with oxidant,the electrons generated by the oxidation unit on the faces of the anodesand cathodes that are opposite the respective faces facing the membrane,referred to as the anode electrons and cathode electrons, respectively,transit via the anode electron collector and via the cathode electroncollector, respectively. To collect more anode electrons and/or cathodeelectrons and thus improve the energy yield of the elementary module,the oxidation unit preferably includes an anode collecting layer, placedon the face of the anode that is opposite the face of the anode facingthe electrolytic membrane, and/or a cathode collecting layer, placed onthe face of the cathode that is opposite the face facing theelectrolytic membrane.

Preferably, the anode collecting layer, respectively, the cathodecollecting layer is separated from the fuel transporter support,respectively, from the oxidant transporter support by the anode chamber,respectively, by the cathode chamber.

The anode collecting layer and/or the cathode collecting layer may be inthe form of a thin film, preferably with a thickness of less than 100μm, which is porous so as to allow the anode feed flow to reach theanode, respectively, to allow the cathode feed flow to reach thecathode. The anode collecting layer and/or the cathode collecting layermay be deposited, respectively, on the face of the anode and/or on theface of the cathode by 3D printing or by vacuum deposition, for examplechemical vapor deposition, or physical vapor deposition. Preferably, theanode collecting layer and/or the cathode collecting layer are formedfrom a metal, preferably from gold.

In particular, the anode collecting layer may occupy between 50% and100% of the area of the face of the anode which it covers and/or thecathode collecting layer may occupy between 50% and 100% of the area ofthe face of the cathode which it covers.

As regards the anode and cathode conductive bridges, they allow,respectively, the transfer of the anode electrons from the anode to theanode electron collector, and of the cathode electrons from the cathodeto the cathode electron collector.

In particular, the anode conductive bridge may be attached by bonding tothe anode and/or to the anode collecting layer and/or to theelectrolytic membrane. For its part, the cathode conductive bridge maybe attached by bonding to the cathode and/or to the cathode collectinglayer and/or to the electrolytic membrane.

The anode conductive bridge may be placed between the anode and the fueltransporter support so as to partially define the anode chamber, and inparticular at least partially, or even totally, a wall of said anodechamber, notably extending in a transverse direction. For its part, thecathode conductive bridge may be placed between the cathode and theoxidant transporter support so as to partially define the cathodechamber, and in particular at least partially, or even totally, a wallof said cathode chamber, notably extending in a transverse direction.

Preferably, the anode conductive bridge is sandwiched between theoxidation block and the anode electron collector and/or the cathodeconductive bridge is sandwiched between the oxidation block and thecathode electron collector.

Preferably, the anode conductive bridge and/or the cathode conductivebridge at least partially, or even entirely, cover the anode electroncollector and/or the cathode electron collector, respectively. In thisway, the electron transfer between the anode and the anode electroncollector and/or between the cathode and the cathode electron collectoris optimal.

The anode conductive bridge and/or the cathode conductive bridge may bein various forms. They may each be in the form of at least one stud orof at least one continuous or discontinuous strip, or of at least onesurface extending in two perpendicular directions.

The studs or strips may form a regular or even periodic pattern. Forexample, the studs may be arranged in a network formed by the periodicrepetition in two perpendicular directions of a square pattern, and ateach apex of one of the patterns of the network. A stud may be in theform of a right prism, notably with a square or rectangular base, or inan axisymmetric cylindrical form. The diameter of the stud,corresponding to the longest length in a direction perpendicular to thegeneratrix of the prism, may be between 0.1 mm and 10 mm. In the variantin which the anode conductive bridge and/or the cathode conductivebridge are in the form of at least one strip, preferably, the width ofat least one, preferably of each, of the strips is between 0.1 mm and 10mm.

In particular, the ratio of the area of the projection of the anodeconductive bridge to the area of the projection of the fuel transportersupport may be between 1% and 50% and/or the ratio of the area of theprojection of the cathode conductive bridge to the area of theprojection of the fuel transporter support may be between 1% and 50%,said projections being made on the longitudinal plane on which extendsthe elemental module and in a transverse direction with respect to saidlongitudinal plane.

The anode conductive bridge and/or the cathode conductive bridge mayhave a thickness of between 1 μm and 100 μm. In particular, the anodeconductive bridge may project from the face of the anode on which it isplaced and/or the cathode conductive bridge may project from the face ofthe cathode on which it is placed.

Moreover, in the variant in which the anode conductive bridge,respectively, the cathode conductive bridge is in the form of at leastone discontinuous strip, the space defined between the two portions ofthe strip and extending between planes parallel to the side faces of thestrip may be at least partially, or even totally, filled with an anodeinsulating bridge, respectively, a cathode insulating bridge. The anodeconductive bridge and the anode insulating bridge may at least partiallydefine a transverse wall of the anode chamber, for example entirelysurrounding the anode chamber, and/or the cathode conductive bridge andthe cathode insulating bridge may at least partially define a transversewall of the cathode chamber, for example entirely surrounding thecathode chamber.

The anode conductive bridge and/or the cathode conductive bridge may beformed on the anode block and/or on the cathode block, respectively, oron the oxidation unit by printing with a glue including the electricallyconductive adhesive, for example by screen printing, by spraying or bydispensing.

The anode conductive bridge and the cathode conductive bridge eachcontain an electrically conductive adhesive.

The electrically conductive adhesive may notably have anisotropicconductivity. Preferably, the anode conductive bridge, respectively, thecathode conductive bridge is such that the direction of greatestelectrical conductivity of the electrically conductive adhesive isparallel to the direction normal to the thickness of the anodeconductive bridge, respectively, of the cathode conductive bridge.

Preferably, the electrically conductive adhesive includes, or evenconsists of, a polymer resin in which are dispersed carbon particles,for example in the form of graphene, and/or metal particles. Preferably,the metal particles comprise, or even consist of, a metal chosen fromsilver, gold and alloys thereof, or are formed from a metal core,preferably made of a metal chosen from copper and nickel and alloysthereof, covered with a carbon coating or a metal coating, preferablymade of a metal chosen from gold, silver and alloys thereof.

In particular, the electrically conductive adhesive of the anodeconductive bridge may be identical to or different from the electricallyconductive adhesive of the cathode conductive bridge.

For example, by way of illustration, the adhesive may be Le TRA-DUCT2902 sold by the company Tra-Con.

For its part, the oxidation unit is preferably placed between the anodeblock and the cathode block.

Preferably, the oxidation unit extends in a plane parallel to orcoincident with the longitudinal plane. In particular, the oxidationunit may be in the form of a composite plate and/or each of the anode,cathode and electrolytic membrane may be in the form of a plateextending in a plane parallel to the longitudinal plane.

In particular, the thickness of the oxidation unit may be greater thanor equal to 0.01 mm and/or less than or equal to 0.5 mm.

Preferably, the anode and/or the cathode are attached to theelectrolytic membrane, for example by drying of an ink deposited byspraying onto the anode, respectively, the cathode and/or the membrane,and containing catalysts based on platinized carbon (C/Pt).

The anode may include, or even may consist of, a mixture of C/Pt and ofNafion, and/or the membrane may be at least partially, or even totally,formed from Nafion, and/or the cathode may include, or even may consistof, a mixture of C/Pt and of Nafion.

Moreover, as regards the fuel transporter support and the oxidanttransporter support, preferably at least one of them, preferably both ofthem, extend in a plane parallel to the longitudinal plane.

Preferably, the fuel transporter support and/or the oxidant transportersupport may each be in the form of a plate. Such fuel transportersupports and/or oxidant transporter support are thus easy, quick andinexpensive to manufacture.

The fuel transporter support and the oxidant transporter support areconfigured to introduce, respectively, the anode feed flow containingthe fuel into the anode chamber and the cathode feed flow containing theoxidant into the cathode chamber. Preferably, the oxidant transportersupport, respectively, the fuel transporter support is porous, so thatthe fuel and the oxidant can entirely pass through the fuel transportersupport, respectively, the oxidant transporter support. To this end, thefuel transporter support and/or the oxidant transporter support mayinclude holes, for example piercings, which pass through the fueltransporter support and/or the oxidant transporter support,respectively, in their respective thicknesses. As a variant, the fueltransporter support and/or the oxidant transporter support may each bein the form of a foam having an open and percolating porosity at leastin the direction of its thickness. In this way, the anode feed flowand/or the cathode feed flow can flow in the thickness of the fueltransporter support and/or of the oxidant transporter support,respectively.

Preferably, the fuel transporter support and/or the oxidant transportersupport are made of an electrically insulating material.

The fuel transporter support and the oxidant transporter support mayinclude, or even may consist of, a polymer material, for example athermoplastic, notably chosen from polyethylene terephthalate PET,polyethylene PE, polycarbonate PC, FR4, Kapton, and mixtures thereof.

In one variant, the fuel transporter support and/or the oxidanttransporter support may be in the form of a flat grate. Preferably, theface of the grate which is facing the anode chamber, respectively, thecathode chamber is at least partially, or even, preferably, entirelycovered with an assembly formed from an electrically insulating film andan electrically conductive metal film defining the anode electroncollector, respectively, the cathode electron collector. Preferably, theelectrically insulating film and, optionally, the electricallyconductive film, is porous, so as to allow the transportation of thefuel or of the oxidant in its thickness. Preferably, the thickness ofthe electrically insulating film and/or the thickness of theelectrically conductive film is between 10 μm and 500 μm. Preferably,the electrically conductive film and the electrically insulating filmcover different portions, which are preferably not superposed, of theface of the grate that is facing the anode chamber, respectively, thecathode chamber. For example, the anode conductive bridge is attached bybonding to the electrically conductive film of the fuel transportersupport forming the anode electron collector and the cathode conductivebridge is attached by bonding to the electrically conductive film of theoxidant transporter support forming the cathode electron collector.Preferably, the anode conductive bridge and/or the cathode conductivebridge are placed at a distance from the electrically insulatingconductive film of the fuel transporter support, respectively, of theoxidant transporter support.

As described previously, an anode electron collector and a cathodeelectron collector are attached, preferably by bonding, to the fueltransporter support and to the oxidant transporter support,respectively. At least one end of the anode electron collector,respectively, of the cathode electron collector may project, for examplelaterally, from the elementary module, and may be electrically connectedto a recontacting connector, to connect the elementary module to anelectrical appliance or to another elementary module, for example theconsecutive elementary module of the stack of elementary modules of afuel cell including a plurality of elementary modules.

In one embodiment, the anode electron collector may be printed onto thefuel transporter support and/or the cathode electron collector may beprinted onto the oxidant transporter support, thus forming an anodeblock, respectively, a cathode block. The anode block and/or the cathodeblock thus formed are then in the form of printed circuits, whichfacilitates the manufacture of the elementary module, and notably therelative positioning of said fuel and oxidant transporter supportsrelative to the oxidation unit during the assembly of the constituentelements of the elementary module.

Preferably, the anode electron collector and/or the cathode electroncollector are at least partially in the form of strips spaced apart fromeach other, preferably forming a regular or even periodic pattern, forexample a grid. For example, the strip(s) extend laterally in thelongitudinal plane, and notably between two opposite side faces of theelementary module.

Moreover, the ratio R of the area S_(A) of the projection of the anodeelectron collector to the area S of the projection of the fueltransporter support is preferably between 0.01 and 0.50, and/or theratio R′ of the area S′_(A) of the projection of the cathode electroncollector to the area S′ of the projection of the fuel transportersupport is between 0.01 and 0.50, said projections being made on thelongitudinal plane and in a transverse direction relative to saidlongitudinal plane. The ratios R and R′ may be identical or different.

Thus, the contact resistance between the anode electron collector and/orthe cathode electron collector, on the one hand, and the oxidation unit,on the other hand, is reduced.

Preferably, the anode electron collector, respectively, the cathodeelectron collector projects, preferably in a transverse direction, fromthe face of the fuel transporter support, respectively to the thicknessof the oxidant transporter support onto which it is attached, the heightof said projection being, for example, equal to the thickness of saidanode electron collector, respectively, of the cathode electroncollector. The anode electron collector, respectively, the cathodeelectron collector thus at least partially defines a spacer separatingthe fuel transporter support, respectively, the oxidant transportersupport from the oxidation unit, said spacer partially defining theanode chamber, respectively, the cathode chamber.

Preferably, the thickness of the anode electron collector and/or thethickness of the cathode electron collector is less than 100 μm.

The anode electron collector and/or the cathode electron collector arepreferably metallic, and may notably include, for more than 99.0% oftheir mass, carbon and/or a metal chosen from silver, tantalum,molybdenum, copper and alloys thereof. Such a metal or alloy readilyconducts the electrons collected on the anode and cathode. In onevariant, the anode electron collector and/or the cathode electroncollector may include a layer formed from said metal, attached to thefuel transporter support, respectively, to the oxidant transportersupport, covered with a protective and conductive film formed fromanother metal or with a superposition of layers, each layer being madeof a metal different from that of the other layers of the film, saidfilm possibly having a thickness of less than 10 μm.

Moreover, as has been described previously, the elementary module mayinclude an anode insulating bridge and/or a cathode insulating bridge,the cathode insulating bridge being formed from at least oneelectrically insulating material. Preferably, the anode insulatingbridge is placed between the oxidation unit and the anode electroncollector. It may be in direct contact with the oxidation unit and withthe anode electron collector. Preferably, the cathode insulating bridgeis placed between the oxidation unit and the cathode electron collector.It may be in direct contact with the oxidation unit and with the cathodeelectron collector.

Preferably, the anode insulating bridge and/or the cathode insulatingbridge are in the form of a thin film, for example having a thickness ofbetween 1 μm and 100 μm. Preferably, the anode insulating bridge and/orthe cathode insulating bridge are placed, respectively, on a portion ofthe face of the anode electron collector facing the oxidation unitand/or on a portion of the face of the cathode electron collector facingthe oxidation unit, said portion(s) being different from portionscovered with the anode conductive bridge and/or with the cathodeconductive bridge. The anode insulating bridge, respectively, thecathode insulating bridge thus protects the portion of the face of theanode electron collector, respectively, of the cathode electroncollector, which is not covered with the anode conductive bridge,respectively, with the cathode conductive bridge.

Notably, the anode insulating bridge and/or the cathode insulatingbridge may be in the form of one or more interrupted strips, studs,notably forming a regular pattern, such as a grid.

For its part, the anode chamber, respectively, the cathode chamber ispreferably placed between the fuel transporter support, respectively,the oxidant transporter support, and the oxidation unit.

Preferably, the anode chamber and/or the cathode chamber extend in aplane parallel to the longitudinal plane. Preferably, the anode chamberis at least partially or even entirely defined by:

-   -   the outer face of the anode opposite the face that is in contact        with the electrolytic membrane, and preferably extending in a        plane parallel to the longitudinal plane,    -   the face of the fuel transporter support that is facing the        outer face of the anode, and preferably extending in a plane        parallel to the longitudinal plane, and    -   the anode leakproofing bridge.

The anode chamber is configured such that when it is fed with fuel, thefuel pressure in the chamber is greater than the atmospheric pressure,which makes it possible to ensure an efficient oxidation reaction of thefuel in the oxidation unit. Preferably, the anode leakproofing bridgedefines a fuel-leaktight seal extending transversely relative to thelongitudinal plane between the anode block and the oxidation unit andsurrounding, preferably entirely, the anode chamber in a plane parallelto the longitudinal plane. In this way, the anode leakproofing bridgereduces the fuel leaks out of the anode chamber by flow of the fluid indirections contained in the longitudinal plane.

Preferably, the anode conductive bridge and/or the anode leakproofingbridge are configured so as to avoid detachment of the oxidation unitfrom the anode block, when the fuel pressure is between 0.1 bar and 5bar. A person skilled in the art readily knows how to determine theproperties of the fuel-leaktight electrically insulating adhesive and/orof the electrically conductive adhesive and to define the dimensions ofthe anode conductive bridge and/or of the anode leakproofing bridge forthis purpose.

Preferably, the anode leakproofing bridge is attached by bonding to theanode and/or to the anode collecting layer and/or to the electrolyticmembrane. The anode leakproofing bridge may notably be obtained byprinting with a glue including the fuel-leaktight electricallyinsulating adhesive, notably by screen printing, or spraying ordispensing or applying an adhesive film.

The fuel-leaktight electrically insulating adhesive may notably bechosen from polyurethane-type or epoxy-type adhesives. For example, itmay be the glue IRS 2125 sold by the company Intertronics.

The anode leakproofing bridge may be in various forms. It is preferablyin the form of a continuous strip, which is preferably closed on itselfand in contact with each of the opposite longitudinal faces of the anodechamber.

Moreover, the elementary module may include a reservoir having aninternal volume for containing the fuel, the anode chamber being influid communication with the internal volume of the reservoir by meansof the fuel transporter support. Thus, the reservoir defines a fuelreserve for ensuring the feeding of fuel to the anode chamber.

Preferably, the fuel transporter support defines a wall of thereservoir. In one embodiment, the reservoir and the fuel transportersupport may form a monolithic block.

Preferably, the reservoir includes a filling orifice configured to beconnected, for example by means of a pipe, to a fuel feed pump or to afuel generating cartridge, for example to a cartridge for generatingdihydrogen by hydrolysis of hydrides. Preferably, in the configurationof the elementary module in which the filling orifice is hermeticallyclosed, the assembly formed by the internal volume of the reservoir andthe volume of the anode chamber is hermetically closed andfuel-leaktight.

For their part, in one embodiment, the oxidant transporter support andthe oxidation unit may be both attached by bonding to each other andelectrically insulated from each other by means of a cathode attachmentbridge containing an electrically insulating adhesive. The electricallyinsulating adhesive of the cathode attachment bridge may be identical toor different from the electrically insulating adhesive of the anodeleakproofing bridge.

Thus, the cathode attachment bridges and/or cathode conductive bridgeensure at least partially, preferably entirely, the mechanical strengthof the connection between the oxidant transporter support and theelectrolysis unit.

Moreover, preferably, the cathode attachment bridge may define atransverse wall of the cathode chamber, which may be closed on itself soas to define an oxidant-leaktight seal, or, on the contrary, may haveapertures, so as to facilitate the flow of the oxidant out of or intothe cathode chamber.

Moreover, the elementary module may include a plurality of electrolysisunits sharing the same electrolytic membrane and preferably being placedin a planar arrangement. As a variant, it may include a singleelectrolysis unit.

The elementary module may also include a gas diffusion layer, preferablyplaced on a face of the oxidant transporter support opposite the facethat is facing the anode chamber, and covered with a porous grate. Thegas diffusion layer and the grate participate in maintaining a level ofhumidity suitable for generating electricity. The gas diffusion layermay be electrically insulating or, on the contrary, may be electricallyconductive. It may be hydrophilic or, on the contrary, hydrophobic. Theporous grate may be metallic, and optionally covered with anelectrically insulating material, or may be made of plastic.

The elementary module may be configured to generate an electric power ofbetween 1 W and 500 W.

The mass of the elementary module may be between 1 g and 1000 g.

As regards the fuel cell, preferably, each elementary module of theplurality of modules extends in an oblique longitudinal plane, which ispreferably perpendicular to the stacking direction.

The elementary modules of the cell may be electrically connectedtogether in series or in parallel.

The cell may include at least two, at least 10, at least 20 elementarymodules.

Preferably, the fuel cell is free of means for compressing the pluralityof elementary modules. In particular, the fuel cell may be free of endplates placed at the opposite ends of the stack and notably connected byat least one compression member.

For example, the stack may include a chassis in the form of a shelfincluding a plurality of pigeonholes placed one after the other in thestacking direction, each pigeonhole extending in a transverse plane withrespect to the stacking direction. Preferably, at least one or even,preferably, several pigeonholes are configured to each house at leastone elementary module. In particular, at least two consecutive modulesof the stack may be separated from each other. In this way, theelementary modules of the stack are not resting on each other, theweight of each elementary module being supported by the chassis.Replacing a defective elementary module is thus facilitated.

In one embodiment, the elementary modules may be spaced apart from eachother in the stacking direction, in a regular, notably periodic, manner.

Moreover, preferably, at least two consecutive modules of the stack areplaced head to tail in the stacking direction. As will be detailedhereinbelow, this arrangement makes it possible to limit the number ofmembers required to feed the stack of elementary modules with fueland/or with oxidant.

Moreover, the cell may include at least one means for generating theoxidant feed flow, and optionally a means for generating the fuel feedflow, so as to ensure the generation of electrical energy by the atleast one elementary module. It may also include at least one means, forexample a fan, for generating a cooling flow, so as to recover byconvective exchange the heat generated by the at least one elementarymodule during the oxidation reaction of the fuel.

Preferably, the cell is configured to define at least one cathode feedchannel configured to transport the cathode feed flow containing theoxidant to at least one elementary module, and/or at least one coolingchannel configured to transport a cooling flow including a heat transferfluid, preferably air, so as to exchange heat by convection with the atleast one elementary module.

In particular, the cathode feed channel and/or the cooling channel mayhave a tubular shape, extending in a direction contained in a planeparallel to the longitudinal planes along which extend the elementarymodules between which is placed the cathode feed channel and/or thecooling channel, respectively. Preferably, the cathode feed channel isdefined by two side faces, which are preferably parallel to the stackingdirection, opposite the cell and by the side faces facing the elementarymodules between which said channel is placed. The pressure lossassociated with the tubular shape of the cathode feed channel and/or ofthe cooling channel is low and the fuel cell may be free of means forgenerating the cathode feed flow and/or the cooling flow, respectively.

As a variant, the cathode feed channel and/or the cooling channel mayhave a form including a plurality of tube portions connected via bentportions. The tube portions may, for example, run to and fro between theopposite side faces of the cell. Such bent forms notably promote theheat exchange in the cooling channel. As a variant, the cathode feedchannel and/or the cooling channel may each be formed from a pluralityof coils extending between the inlet and outlet apertures of saidcathode feed channel and/or of said cooling channel, respectively, thecoils being parallel to each other. In another variant, the cathode feedchannel is formed from a plurality of tubes, two neighboring tubessharing a common wall. In particular, the tubes of the plurality may beparallel to each other and may be placed between the faces that arefacing two consecutive elementary modules. Such forms of cathode feedchannel and/or of cooling channel promote the feeding of oxidant and/orthe heat exchange, respectively. Preferably, to compensate for thepressure loss associated with the presence of multiple internal wallsand/or bends in the cathode feed channel and/or in the cooling channel,the fuel cell may include a cathode feed flow generator and/or a coolingflow generator, respectively, preferably including a compressor.

In particular, the cooling flow generator and/or the cathode feed flowgenerator may be chosen from a fan, notably an axial or radial fan, aturbine and a compressor.

In the preferred variant in which the oxidant is dioxygen, the cathodefeed flow is preferably a flow of air. In particular, the cooling flowgenerator and/or the cathode feed flow generator may function byextracting or blowing air, in a continuous regime or in pulse widthmodulation (PWM) mode.

Moreover, the cell may include one or more cooling flow generatorsand/or one or more cathode feed flow generators. For example, the fuelcell may include a plurality of cooling flow generators such that eachof the generators of the plurality feeds a single couple formed from twoelementary modules.

Preferably, the at least one elementary module is placed between thecathode feed channel and the cooling channel. Preferably, the cathodefeed channel extends in an oblique extension direction, preferablyorthogonal to the extension direction in which extends the coolingchannel. Preferably, the planes in which generally extend the cathodefeed channel and the cooling channel are different and parallel, andpreferably perpendicular to the stacking direction.

Preferably, the cathode feed channel has at least one inlet aperture,respectively, at least one outlet aperture, for the cell inlet,respectively, outlet flow of the cathode feed flow, and the coolingchannel has at least one inlet aperture, respectively, at least oneoutlet aperture, for the cell inlet, respectively, outlet flow of thecooling flow, the inlet apertures and outlet apertures of said cathodefeed channels and cooling channels being configured so that the cellinlet and outlet cathode feed flows flow in at least one oblique,preferably perpendicular, direction with respect to the at least onedirection of flow of the cell inlet and outlet cooling flows.

Preferably, the inlet apertures and outlet apertures of said cathodefeed channel and cooling channel are configured so that the direction(s)of flow of the cell inlet and outlet cathode feed flows and thedirection(s) of flow of the cooling flows are contained in different andparallel planes, which are preferably perpendicular to the stackingdirection.

Via any one of the features described in the three immediately precedingparagraphs, the risks of interaction between the cathode feed flow andthe cooling flow, which may have a negative impact on the energy yieldof the cell, are thus limited.

The inlet apertures and outlet apertures of said cathode feed channeland cooling channel may have various shapes. For example, they have acircular, rectangular, square or oval contour.

Moreover, the cooling channel and/or the cathode feed channel may haveseveral inlet apertures and/or several outlet apertures.

The shape and/or sizes of the inlet aperture of the cooling channel maybe identical to or different from the shape and/or sizes of the outletaperture of the cooling channel. The shape and/or sizes of the inletaperture of the cathode feed channel may be identical to or differentfrom the shape and/or sizes of the outlet aperture of the cathode feedchannel.

The shape and/or sizes of the inlet and outlet apertures of the coolingchannel may be identical to or different from the shape and/or sizes ofthe inlet and outlet apertures of the cathode feed channel.

Moreover, the cathode feed channel may be placed between the respectivecathode blocks of at least two consecutive elementary modules of theplurality of elementary modules in the stacking direction, and may beconfigured to transport the cathode feed flow to the oxidant transportersupport of each of said two respective elementary modules, and/or thecooling channel may be placed between at least two consecutiveelementary modules of the plurality of elementary modules in thestacking direction and is configured to transport the cooling flow so asto exchange heat by convection with said two elementary modules. Thus, acathode feed channel may feed several elementary modules and/or acooling channel may exchange heat with several elementary modules. Themass of the oxidant feed means and of the cooling means of the fuel cellis thus limited.

Moreover, the fuel cell preferably includes:

-   -   a plurality of cathode feed channels, each cathode feed channel        being configured to feed at least one elementary module with        cathode feed flow,    -   a cathode feed probe placed in a channel of the plurality of        cathode feed channels and configured to measure at least one        cathode feed property chosen from the humidity, the temperature        and the pressure,    -   a cathode feed flow generator configured to generate the cathode        feed flow to be transported in said channel or in another        channel of the plurality of cathode feed channels, and    -   a unit for controlling said cathode feed flow generator, which        is configured to regulate, as a function of the measurement of        the cathode feed property, at least one parameter of said        cathode feed flow to be transported in said channel and/or said        cathode feed flow to be transported in the other channel.

The at least one parameter of said cathode feed flow may be chosen fromthe temperature, the pressure, the flow rate, the speed of the cathodefeed flow at the cathode feed flow generator outlet, and combinationsthereof.

Preferably, the fuel cell includes:

-   -   a plurality of cooling channels, each cooling channel being        configured to transport a cooling flow so as to exchange heat by        convection with at least one elementary module,    -   a cooling probe placed in a channel of the plurality of cooling        channels and configured to measure at least one cooling property        chosen from the humidity, the temperature and the pressure,    -   a cooling flow generator configured to generate the cooling flow        to be transported in said channel or in another channel of the        plurality of cooling channels, and    -   a unit for controlling said cooling flow generator, which is        configured to regulate, as a function of the measurement of the        cooling property, at least one parameter of said cooling flow to        be transported in said channel and/or said cooling flow to be        transported in the other channel.

In this way, the temperature of the oxidation units of each elementarymodule is regulated, for example, by means of a limited number ofsensors, in particular by means of a single sensor.

The at least one parameter of said cooling flow may be chosen from thetemperature, the pressure, the flow rate, the speed of the cooling flowat the cooling flow generator outlet, and combinations thereof.

Moreover, the fuel cell may include a sensor placed in an elementarymodule in fluid communication with the cathode feed channel in which isplaced the cathode feed probe and/or which is capable of exchanging heatby convection with a cooling flow flowing in the cooling channel inwhich is placed the cooling probe, said sensor being configured tomeasure an electrical resistance chosen from an internal resistance ofthe cell, the polarization resistance of the cell, or the totalresistance of the cell. Preferably, the unit for controlling saidcathode feed flow generator is configured to regulate, as a function ofthe measurement of the cathode feed property and of the measurement ofthe electrical resistance, at least one parameter of said cathode feedflow to be transported in said channel and/or said cathode feed flow tobe transported in the other channel, and/or the unit for controllingsaid cooling flow generator is configured to regulate, as a function ofthe measurement of the cooling property and of the measurement of theelectrical resistance, at least one parameter of said cooling flow to betransported in said cooling channel and/or said cooling flow to betransported in the other cooling channel.

In one embodiment, the fuel cell includes at least one diaphragm and/orat least one flap configured to limit the flow rate at the inlet of thecathode feed channel and/or of the cooling channel. For example, in avariant in which the fuel cell is placed in a flying object, the airmovements during a flight of the flying object may bring about theformation of spurious flows which may modify the behavior of the cell.In such an embodiment, one means for generating cathode feed flowsand/or cooling flows may be the movement of the flying object.Preferably, all the flaps and/or diaphragms are controlled by a singleflap and/or diaphragm control module configured to place the flapsand/or diaphragm in the same open or closed configuration. The flapsand/or diaphragms may all be placed facing a side face of the cell. Inparticular, the flaps and/or diaphragms placed facing the coolingchannel apertures may be placed facing the same face as the flaps and/ordiaphragms placed facing the cathode feed channel apertures. In onevariant, flaps and/or diaphragms may be placed on other side faces, andnotably on an opposite face.

As regards its dimensions, the cell may have a height of between 20 mmand 600 mm and/or a width of between 20 mm and 600 mm, and/or a depth ofbetween 20 mm and 600 mm.

Finally, the mass of the fuel cell may be between 0.01 kg and 10 kg. Thefuel cell is configured to generate an electric power of between 1 W and50 kW.

Preferably, the cell has a power density per unit mass of between 100W·kg⁻¹ and 5000 W·kg⁻¹.

The invention also relates to a process for manufacturing a fuel cellaccording to the invention, including a step of manufacturing at leastone elementary module, preferably according to either of the first andsecond aspects of the invention, the step for manufacturing theelementary module including the attachment, preferably the bonding, ofan anode block, respectively, of a cathode block, to an oxidation unit.

Preferably, at least two, preferably at least 10, elementary modules aremanufactured, and the elementary modules are stacked on top of eachother in a stacking direction.

Preferably, at least one adhesive composition is deposited on the anodeblock, respectively, on the cathode block, and/or on the oxidation unit,and the anode block, respectively, the cathode block is then assembledwith the oxidation unit so as to form an attachment bridge rigidlyattached to the anode block, respectively, to the cathode block, and tothe oxidation unit.

The adhesive composition may have a liquid or solid form.

Other features and advantages of the invention will also emerge onreading the detailed description that follows and from the attacheddrawing, in which:

FIGS. 1 to 5 schematically represent, in cross section view, differentimplementation variants of an elementary module according to theinvention,

FIG. 6 schematically represents a fuel cell including a plurality ofelementary modules according to the invention, in cross section viewalong the stacking direction of the elementary modules,

FIGS. 7 to 9 schematically represent in perspective variants of fuelcells according to the invention, and

FIG. 10 is a photograph of a cell according to one embodiment of theinvention.

In the various figures, identical references are used to denoteidentical or similar members.

The elementary module 5 of FIG. 1 extends in a longitudinal plane Pincluding a longitudinal direction X. It includes an oxidation unit 10formed from a stack constituted successively of an anode 15, of anelectrolytic membrane 20 and of a cathode 25, all three each being inthe form of a plate extending in a plane parallel to the longitudinalplane. The electrolysis unit is placed between an oxidant transportersupport 30 and a fuel transporter support 35, each being in the form ofa porous plate extending in a plane parallel to the longitudinal planeof the elementary module.

A cathode electron collector 40, in the form of a strip projecting in atransverse direction T relative to the longitudinal plane, is attachedto the oxidant transporter support, thus defining with the oxidanttransporter support a cathode block 45. It is attached to the cathode bymeans of a cathode conductive bridge 50 formed from an electricallyconductive adhesive. The cathode conductive bridge extends in thetransverse direction between two opposite faces 55 and 60, one of them55 being in contact with the cathode electron collector, the other 60being in contact with the cathode. Thus, the oxidation unit and thecathode block are attached to each other by bonding and electricallyconnected.

Moreover, the oxidant transporter support, the cathode electroncollector, the cathode conductive bridge and the cathode define acathode chamber 65. Thus, during functioning, the cathode feed flow, forexample generated by a fan and transported in a cathode feed channel, aswill be described hereinbelow, passes through the porous oxidanttransporter support, as indicated by the arrow O to penetrate into thecathode chamber and come into contact with the cathode so as to ensurethe oxidation reaction of the fuel. The cathode electrons resulting fromthe oxidation reaction which are formed at the cathode may be collectedand then, as indicated by the arrow Ec, may then be transferred by meansof the cathode collector bridge to the cathode electron collector.

An anode electron collector 70, in the form of a strip projecting in thetransverse direction, is attached to the fuel transporter support 35,thus defining with the fuel transporter support an anode block 75. Theanode electron collector is attached to the anode by means of an anodeconductive bridge 80 formed from an electrically conductive adhesive.The anode conductive bridge extends in the transverse direction betweentwo opposite faces 85 and 90, one of them 90 being in contact with theanode electron collector, the other 85 being in contact with the anode.Thus, the oxidation unit and the anode block are attached to each otherby bonding. In addition, the anode electrons resulting from theoxidation reaction of the fuel, which are formed at the anode, may becollected and then, as indicated by the arrow Ea, may then betransferred by means of the anode conductive bridge to the anodeelectron collector.

In this way, the attachments by bonding of the anode and cathode blocksby means of the respective anode and cathode conductive bridges to theoxidation unit ensure the mechanical strength of the elementary module,without it being necessary to insert permanent compression means forthis purpose.

Moreover, an anode leakproofing bridge 100, formed from a fuel-leaktightelectrically insulating adhesive seal, is sandwiched between the anodeblock and the fuel transporter support and holds them a distance fromeach other, defining an anode chamber 105 extending in a plane parallelto the longitudinal plane. The anode leakproofing bridge forms aleakproofing seal extending between the faces facing the anode and thefuel transporter support, in a transverse direction relative to thelongitudinal plane. The anode leakproofing bridge surrounds said anodechamber in a plane parallel to the longitudinal plane. Besides itsleakproofing function described hereinbelow, it reinforces themechanical strength of the elementary module, by adding an additionalattachment between the anode block and the oxidation unit. Duringfunctioning, the attachment of the oxidation unit by means of the anodeleakproofing bridge and the anode conductive bridge allows theelementary module to withstand the fuel pressure in the anode chamber,which is above atmospheric pressure.

Moreover, the elementary module includes a reservoir 108, defining aninternal volume 110, including a filling orifice 115 for feeding thereservoir with fuel. The fuel transporter support moreover defines awall 118 separating the anode chamber from the internal volume of thereservoir.

During functioning, a compressor can inject a fuel flow into theinternal volume of the reservoir via the filling orifice, in which thefuel is thus stored. The anode feed flow containing the fuel then passesthrough the fuel transporter support, which is porous, and penetratesinto the anode chamber where it flows, in a transverse directionrelative to the longitudinal direction, until it comes into contact withthe anode, as indicated by the arrow C. The anode leakproofing bridgelimits the flow of the fuel flow in the chamber in any directioncontained in the longitudinal plane, as indicated by the arrows L₁ andL₂, and thus reduces the leaks of fuel out of the anode chamber.

The elementary module of FIG. 2 differs from the elementary module ofFIG. 1 in that an anode collecting layer 120 and a cathode collectinglayer 125 are placed on the faces 130 and 135 of the anode and cathode,respectively, placed facing the anode and cathode chambers,respectively.

The anode and cathode collecting layers improve the collection of theanode and cathode electrons generated remotely from the anode andcathode electron collectors, respectively.

In order for the fuel and the oxidant to be able to come into contactwith the anode and the cathode, respectively, the electron collectinglayers may partially cover said faces of the anode and cathode and, forexample, may be fuel-leaktight or oxidant-leaktight, respectively. Inthis variant, the fuel and the oxidant may come into contact with theanode and the cathode, respectively, in the zones of said faces of theanodes and cathodes that are not covered with the anode and cathodecollecting layers, respectively. The anode and cathode collecting layersmay also be in the form of a film that is porous with respect to thefuel and to the oxidant, respectively, and which covers, for exampleentirely, said faces of the anode and cathode, respectively.

In the example of FIG. 2, the anode conductive bridge 80 and the anodeleakproofing bridge 100 are attached by bonding to the anode layer.

Moreover, to further reinforce the mechanical strength of the elementarymodule, the elementary module of FIG. 2 includes a cathode attachmentbridge 140 formed from an electrically insulating adhesive, extendingbetween two opposite faces of the cathode chamber in a transversedirection relative to the longitudinal plane, one of the faces 145 ofthe cathode attachment bridge being bonded to the oxidant transportersupport, the other face 150 of said bridge being bonded to the cathodecollecting layer 125.

Although this is not illustrated, the elementary module of FIG. 1 mayinclude such a cathode attachment bridge bonded both to the fueltransporter support and to the cathode.

The elementary module of FIG. 3 differs from the elementary module ofFIG. 2 in that the anode, respectively, the cathode includes an anodewindow 155, respectively, a cathode window 160, passing through theanode, respectively, the cathode, in its thickness, and lying on theelectrolytic membrane. The anode conductive bridge 80, respectively, thecathode conductive bridge 50 is housed in the anode window,respectively, in the cathode window, and is attached by bonding to theelectrolytic membrane 10.

In the variant in which the mechanical connection between the anode,respectively, the cathode and the electrolytic membrane is weak, themechanical strength of the elementary module is improved, theconnections of the anode and cathode blocks, respectively, by means ofthe anode and cathode conductive bridges, respectively, with theoxidation unit being made directly with the electrolytic membrane.

The anode conductive bridge 80, respectively, the cathode conductivebridge 50 has a relief 165, respectively, 170 projecting longitudinallyand being placed in contact with the anode collecting layer,respectively, with the cathode collecting layer. The relief of the anodeconductive bridge, respectively, of the cathode conductive bridge placesthe anode, respectively, the cathode in electrical contact with theanode electron collector, respectively, with the cathode electroncollector.

FIG. 4 illustrates an embodiment of the fuel cell including severalelementary modules 5 ₁, 5 ₂ sharing the same electrolytic membrane 20.Relative to a cell constituted of two modules each placed on differentelectrolytic membranes, each of said two modules being as illustrated inFIG. 3, the arrangement illustrated in FIG. 4 makes it possible toincrease the voltage delivered by the cell for the same power generated.The fuel cell of FIG. 4 includes elementary modules as illustrated inFIG. 3, which may obviously be combined and/or replaced with one or moreelementary modules, for example as illustrated in FIGS. 1 and 2.Moreover, in a variant not shown, the elementary modules may share thesame fuel transporter support and/or the same insulating transportersupport. They may or may not share the same reservoir.

FIG. 5 illustrates a fuel cell including an elementary module asillustrated in FIG. 2, also including a superposed porous gas diffusionlayer 170 which is in contact with the face of the oxidant transportersupport opposite the face that is facing the anode chamber. Moreover,the gas diffusion layer is placed between the oxidant transportersupport and a porous grate 175 with which it is in contact.

The fuel cell of FIG. 5 also includes a first hollow tube 180, one wallof which is at least partially formed by the grate 175, which defines acathode feed channel 185 for transporting a cathode feed flow includingthe oxidant. The hollow tube includes an inlet aperture 190 for thecathode feed flow, as indicated by the arrow O_(E), which is placedfacing a fan 200 that is capable of generating said cathode feed flow.The hollow tube moreover includes an outlet aperture 205, via which thecathode feed flow can escape, as indicated by the arrow O_(S) after ithas passed through the porous grate 175 and the gas diffusion layer andafter having fed, as indicated by the arrow O, the cathode chamber 65 ofthe elementary module, and after having been charged with oxidationreaction products. In particular, in the case where the oxidant isdioxygen and the fuel is dihydrogen, the oxidation reaction produceswater vapor which is evacuated from the anode chamber to the outletaperture by the cathode feed flow, in the present case a flow of air.

The fuel cell also has a second hollow tube 210 placed such that theelementary module 5 is sandwiched between the first 185 and second 210hollow tubes. The second hollow tube has a wall in common with thereservoir. It defines a cooling channel 212 having an inlet aperture 215configured for the inlet of a cooling flow R including a heat transferfluid such as air, placed facing a fan 220 configured to generate anddistribute said cooling flow to said inlet aperture.

When it flows in the cooling channel as indicated according to the arrowR, the elementary module exchanges heat generated by the exothermicoxidation reaction by convection on the wall 225 common to the moduleand to the second hollow tube. The cooling flow thus heated flows to anoutlet aperture 230 placed opposite the inlet aperture, via which it isevacuated from the fuel cell.

As may be seen in FIG. 5, in order to avoid any interaction between thecathode feed flow O and the cooling flow R, the cathode feed channel andthe cooling channel extend in different planes P₁ and P₂ parallel to thelongitudinal plane.

Moreover, in the example of FIG. 5, the fan for generating the coolingflow and the fan for generating the cathode feed flow including theoxidant are placed facing the same side face 235, parallel to thestacking direction D_(E) of the fuel cell. As a variant, the fan forgenerating the cooling flow may be placed on the side face opposite theone to which the fan for generating the cathode feed flow is placedfacing.

In a variant not shown, and notably when the cell is intended forgenerating an electric current within a limited operating temperaturerange, the cell may be free of means as described, for example, in FIG.5, for cooling the cell by means of a cooling flow.

The fuel cell 250 of FIG. 6 includes a plurality of four elementarymodules 5 a-d stacked on each other in a stacking direction D_(E).

Each elementary module of the plurality is identical to that illustratedin FIG. 5, with the exception that the apertures and outlets of thecooling channels are formed on faces perpendicular to those on which areformed the apertures and outlets of the cathode feed channels. Thestacking direction D_(E) is perpendicular to the longitudinal plane P ofeach elementary module.

The fuel cell is configured such that each pair of two consecutiveelementary modules of the stack is such that said two elementarymodules, for example 5 a and 5 b, are arranged head to tail relative toeach other in the stacking direction.

The modules of the stack are electrically connected by means of anelectrical circuit, not shown, connecting an anode electron collector ofone elementary module to a cathode electron collector of an adjacentelementary module.

In the stack of FIG. 6, two consecutive elementary modules havingcathode blocks placed facing each other are separated by a cathode feedchannel 255 ₁₋₂ extending in a transverse plane relative to the stackingdirection. Thus, by means of a single cathode feed channel, the cathodechambers 65 a-d of the two elementary modules are fed with a singlecathode feed flow at the inlet O.

Moreover, two consecutive elementary modules whose anode blocks, forexample 75 b and 75 c, are placed facing each other and are separated bya cooling channel 260 extending in a transverse plane relative to thestacking direction. Thus, by means of a single cooling channel, the twoelementary modules 5 b and 5 c are cooled by convective exchange withthe cooling flow R flowing in the channel.

In this way, the fuel cell 250 of FIG. 6 is configured such that thecathode feed channel and the cooling channel are placed a distance fromeach other and in alternance along the stacking direction D_(E). In thisway, the interactions between the cathode feed flow O and the coolingflow R are limited.

As regards the generation of the cathode feed flows and of the coolingflows, the fuel cell of FIG. 6 includes two cathode feed fans 200 ₁₋₂configured so as each to feed a respective cathode feed channel 255 ₁₋₂with associated cathode feed flows and three cooling fans 220 ₁₋₃configured so as each to feed a cooling channel with associated coolingflows. Moreover, the cathode feed fans and the cooling fans are placedfacing side faces 270, 275 of the cell that are perpendicular to eachother. In this way, the cathode feed flows and the cooling flows flow inrespectively oblique flow directions. The interaction between said flowsis limited, which optimizes the energy yield of the cell.

Moreover, the fuel cell illustrated in FIG. 6 includes a cathode feedprobe 280 placed in one of the cathode feed channels to measure thetemperature of the cathode feed flow in said channel. The cathode feedprobe is electrically connected to a unit 285 for controlling the anodefeed fans of the cell, via connection means not shown, said control unitbeing configured to regulate, as a function of the temperature measuredby the cathode feed probe, for example, the flow rate of the cathodefeed flow at the outlet of each of the cathode feed fans of the fuelcell.

In this way, by means of a single cathode feed probe, the flow rate ofthe cathode feed flows of the plurality of cathode feed channels of thecell can be easily regulated.

The fuel cell of FIG. 6 also includes a cooling probe 292 placed in oneof the cooling channels consecutive to the cathode feed channel in whichis placed the cathode feed probe, to measure the temperature of thecooling flow in said cooling channel. The cooling probe is electricallyconnected to a unit for controlling the cooling fans 298 of the fuelcell, via connection means not shown, said control unit being configuredto regulate, as a function of the temperature measured by the coolingprobe, for example, the flow rate of the cooling flow at the outlet ofeach of the cooling fans of the fuel cell.

In this way, by means of a single cooling probe, the flow rate of thecooling flows of the plurality of cooling channels of the cell can beeasily regulated.

The fuel cell also includes a sensor 300 placed in an elementary moduleto measure, for example, the internal resistance of the elementarymodule. The sensor is connected to the units for controlling the cathodefeed fan and cooling fan which are also each configured to regulate theflow rates of the cathode feed flow and the cooling flow as a functionof the internal resistance measurement of the elementary module.

FIG. 7 schematically shows a fuel cell 250 including six elementarymodules 5 a-f stacked in a stacking direction D_(E), each elementarymodule being thin and extending in a longitudinal plane P normal to thestacking direction.

The elementary modules of the fuel cell are placed head to tail in pairsas in the example of FIG. 6.

The fuel cell of FIG. 7 is in the general form of a right slab havingfour side faces 280 a-d on which emerge the inlets and outlets of thevarious cathode feed channels and cooling channels. In the example ofFIG. 7, each cathode feed channel, respectively, each cooling channelhas an inlet aperture 290 a-c, respectively, 295 a-d emerging on a sideface facing a cathode feed fan 300, respectively, a cooling fan 305, andhas outlet apertures 310 a-c, respectively, 315 a-d emerging on each ofthe other three side faces of the cell.

In the example of FIG. 7, one or more cathode feed fans 300 are placedfacing a side face 280 b perpendicular to another side face 280 atowards which one or more cooling fans 305 are placed facing. Thus, thecathode feed flows O, on the one hand, and the cooling flows R, on theother hand, flow in the respective channels in substantiallyperpendicular directions.

Thus, although each cathode feed channel and each cooling channel haveapertures on the four side faces 280 a-d of the cell, interactions withharmful consequences for the functioning of the fuel cell, betweencathode feed flows and cooling flows, are limited.

The fuel cell of FIG. 8 is an improved and preferred embodiment of thefuel cell of FIG. 7, in which, for each cathode feed channel,respectively, each cooling channel, the apertures formed on the facesperpendicular to those on which is formed the inlet aperture of saidchannel are closed by means of side walls. Thus, the flow of the cathodefeed flow, respectively, of the cooling flow takes place in thedirection of the outlet aperture 310, respectively, 315 emerging on theside face of the cell opposite the side face on which emerges the inletaperture 290, respectively, 295. In this way, the cathode feed flows andcooling flows flow in perpendicular directions and at different heightsin the stacking direction and do not interact. Such an arrangementpromotes the functioning of the fuel cell over an extended operatingtemperature range.

For example, to obtain the cell illustrated in FIG. 8, the sideapertures of each cathode feed channel formed on one, or even on thetwo, side faces of the cell of FIG. 5, perpendicular to the side face onwhich is formed the inlet aperture for the cathode feed flow, may beclosed so as to prevent the outlet of said flow, for example by means ofmasks referenced 320 a-c between the dotted lines, for example made ofpolymer, notably formed from foam. Moreover, the side apertures of eachcooling channel formed on one, or even on the two, side faces of thecell of FIG. 7, perpendicular to the side face on which is formed theinlet aperture for the cooling flow, may be closed so as to prevent theoutlet of said flow, for example by means of masks referenced 325 a-cbetween the dotted lines, for example made of polymer, notably formedfrom foam.

In this way, the cathode feed flows and cooling flows flow inperpendicular directions and do not interfere with each other.

In the example of FIG. 8, two consecutive elementary modules are placedhead to tail. In a variant not shown, two consecutive elementary modulesmay be placed such that the anode block of the first elementary moduleis facing the cathode block of the second elementary module. Preferablythen, in order to separate the cathode feed flow for feeding saidcathode, from the cooling flow, a solid separating plate extending in alongitudinal direction is placed between the two consecutive elementarymodules.

Moreover, the stack of FIG. 8 may be obtained by placing two crossbraces between two consecutive elementary modules. The cross braces are,for example, solid bars. They are spaced apart from each other so as toform the side walls of a cathode feed channel or of a cooling channel.

The fuel cell of FIG. 9 differs from the fuel cell of FIG. 8 in thateach module has a length L at least twice as long as the width 1. Inorder to ensure optimum cooling of the elementary modules, several fansare placed in the longitudinal direction X facing the side face 280 onwhich emerge the apertures 295 a-d of the cooling channels. The discs330 ₁₋₆ schematically indicate the portion of the side face onto whichis directed the cooling flow.

Finally, none of the elementary modules described in FIGS. 1 to 4 andnone of the fuel cells illustrated in FIGS. 5 to 9 includes means forcompressing the plurality of elementary modules, such as clamping platesconnected by compression tie rods.

Example

A fuel cell, a photograph of which is shown in FIG. 10, is formed by astack of 12 elementary modules, each in the form of a thin right slabwith a length of 117 mm, a width of 74 mm and a thickness of 2 mm Thisfuel cell is configured to oxidize dihydrogen as fuel with atmosphericdioxygen.

Each elementary module weighs 8 g and is capable of generating anelectric power of 8 W. Two consecutive elementary modules are placedhead to tail in the stacking direction and are spaced 1.2 mm apart, bymeans of a spacer formed by foam bars, the opposite faces of which, eachin contact with one of said two consecutive modules, are covered withadhesive. The stack is in the form of a right slab, with a length of 117mm, a width of 74 mm and a thickness of 45 mm.

The fuel cell has a volume of 0.4 liter and a mass of less than 150 g.It is capable of generating an electric power of 100 W and has a powerdensity per unit mass of 0.67 W·g⁻¹. It is moreover suitable forgenerating electrical energy over a temperature range of between −20° C.and 50° C.

The fuel cell has an internal resistance of 175 mΩ·cm², similar to thatof a cell of the prior art including end clamping plates and having alower power density per unit mass for the same generated power. Thisinternal resistance value indicates that the collection of electrons andthe electrical connection of the elementary modules is of good quality.

Moreover, the pressure resistance measurements indicate that the fuelcell can withstand a maximum dihydrogen pressure of 3 bar in the anodechamber of each elementary module. In addition, as regards theleaktightness of the anode chamber, the measurements of leaktightness byinfiltration of helium indicate that the rate of leakage is low, lessthan 0.1 cm³/min

For comparative purposes, the performance qualities of the present fuelcell may be compared with a fuel cell formed from a stack of modulescompressed by end plates, sold by the company Horizon FC. This cellfunctions within a lower temperature range of between 0° C. and 40° C.and is capable of generating a power of 200 W. However, it has a mass of470 g and thus a low power density per unit mass equal to 0.42 W·g⁻¹compared with the fuel cell of the invention.

Needless to say, the invention is not limited to the embodiments andexamples described above.

For example, notably in the variant in which the cathode feed channeland/or the cooling channel have bent shapes, for example a coil or aplurality of parallel tubes, the cell may include a compressor, adistribution channel being connected to the compressor, the compressorbeing configured to distribute a cathode feed flow and/or a cooling flowat the inlet of the cathode feed channel and/or of the cooling channel,respectively.

Moreover, preferably, the cooling flow may include a heat transfer fluidother than air, for example a liquid, for example water or an oil.

Moreover, the fuel is not limited to dihydrogen. It may also be analkane chosen, for example, from methane, propane, butane and mixturesthereof, or an alcohol in vapor form chosen, for example, from ethanol,methanol and mixtures thereof. The oxidant is not limited to dioxygen.It may also be a gas including dioxygen, for example air, or a mixtureconstituted of dioxygen and dinitrogen.

Finally, the terms “comprising a”, “containing a” and “including a” areunderstood as equivalently meaning, respectively, “comprising at leastone”, “containing at least one” and “including at least one”.

1. An elementary module of a fuel cell, the elementary module including:an oxidation unit configured to generate electrons by means of theoxidation of a fuel with an oxidant the oxidation unit including ananode and a cathode sandwiching an electrolytic membrane, an anode blockincluding a fuel transporter support suitable for transporting an anodefeed flow containing the fuel to an anode chamber, and an anode electroncollector attached to the fuel transporter support, a cathode blockincluding an oxidant transporter support suitable for transporting acathode feed flow containing the oxidant to a cathode chamber, and acathode electron collector attached to the oxidant transporter support,the elementary module being configured so as to define the anodechamber, respectively, the cathode chamber, between the oxidation unitand the fuel transporter support, respectively, the oxidant transportersupport, the anode electron collector, respectively, the cathodeelectron collector and the oxidation unit being both attached by bondingand electrically connected to each other by means of an anode conductivebridge, respectively, a cathode conductive bridge, containing anelectrically conductive adhesive.
 2. The elementary module as claimed inclaim 1, in which the oxidation unit includes an anode collecting layer,placed on the face of the anode opposite the face that is facing theelectrolytic membrane, and/or a cathode collecting layer, placed on theface of the cathode opposite the face that is facing the electrolyticmembrane.
 3. The elementary module as claimed in claim 1, in which: theanode conductive bridge is attached by bonding to the anode and/or tothe anode collecting layer and/or to the electrolytic membrane, and/orthe cathode conductive bridge is attached by bonding to the cathodeand/or to the cathode collecting layer and/or to the electrolyticmembrane.
 4. The elementary module as claimed in claim 1, in which theanode conductive bridge and/or the cathode conductive bridge partially,or even entirely, cover the anode electron collector and/or the cathodeelectron collector, respectively.
 5. The elementary module as claimed inclaim 1, in which: the anode electron collector and/or the cathodeelectron collector are at least partially in the form of strips spacedapart from each other and/or the anode conductive bridge and/or thecathode conductive bridge are in the form of studs or strips.
 6. Theelementary module as claimed in claim 1, the elementary module extendingin a longitudinal plane, in which: the ratio R of the area S_(A) of theprojection of the anode electron collector to the area S of theprojection of the fuel transporter support is between 0.01 and 0.50,and/or the ratio R′ of the area S′_(A) of the projection of the cathodeelectron collector to the area S′ of the projection of the fueltransporter support is between 0.01 and 0.50, said projections beingmade on the longitudinal plane, and in a transverse direction withrespect to said longitudinal plane.
 7. The elementary module as claimedin claim 1, in which the anode conductive bridge is sandwiched betweenthe oxidation block and the anode electron collector and/or the cathodeconductive bridge is sandwiched between the oxidation block and thecathode electron collector.
 8. The elementary module as claimed in claim1, including: an anode insulating bridge sandwiched between theoxidation unit and the anode collector and/or a cathode insulatingbridge sandwiched between the oxidation unit and the cathode electroncollector, the anode insulating bridge, respectively, the cathodeinsulating bridge being formed from at least one electrically insulatingmaterial.
 9. The elementary module as claimed in claim 1, in which theelectrically conductive adhesive has anisotropic electricalconductivity.
 10. The elementary module as claimed in claim 1, in whichthe electrically conductive adhesive is formed from a polymer resin inwhich are dispersed carbon particles or metal particles.
 11. Theelementary module as claimed in claim 10, in which the particles consistof a metal chosen from silver, gold and mixtures thereof, or are formedfrom a metal core covered with a carbon coating or a metal coating. 12.The elementary module as claimed in claim 1, in which the oxidation unitand the fuel transporter support are both attached by bonding to eachother and electrically insulated from each other by means of an anodeleakproofing bridge containing a fuel-leaktight electrically insulatingadhesive, the anode leakproofing bridge being configured so that theanode feed flow transported to the anode chamber flows essentiallydirectly from the fuel transporter support to the anode.
 13. Theelementary module as claimed in claim 1, including a plurality ofelectrolysis units sharing the same electrolytic membrane.
 14. A fuelcell including an elementary module as claimed in claim 1 or a pluralityof elementary modules stacked on top of each other in a stackingdirection, each elementary module being as claimed in claim
 1. 15. Thefuel cell as claimed in claim 14, being free of means for compressingthe plurality of elementary modules.